Repairing old 10K YG ring

I need to repair an old 10k yellow gold ring shank. I can easily get
8k yellow gold solder but cannot find a source for 10k yg ring shank.
Does anyone know of a source. Can 14k be used for the new section of
ring shank? This isn’t much of a ring but holds great nostalgia for
my brother-in-law.

My experience in jewelry making so far is advanced intermediate. My
orchid is about 2/3 unfolded;-).

Any help/tips most appreciated- I really need it!

I haven’t done much yet with gold due to the price.